1. Field of the Invention
The present invention relates to a speech-duration detector that detects a starting end and a trailing end of speech from an input acoustic signal, and to a computer program product for the detection.
2. Description of the Related Art
A typical speech-duration detection method (a speech-duration detector) detects starting and trailing ends of a speech-duration based on rising/falling of an envelope of a short-time power (hereinafter, “power”) extracted for each frame of 20 to 40 milliseconds. Such detection of starting and trailing ends of a speech-duration is carried out by using a finite state automaton (FSA) disclosed in Japanese Patent No. 3105465.
However, according to the finite state automaton disclosed in Japanese Patent No. 3105465, a single time control parameter is used to detect each of starting and trailing ends. When noise extemporaneously occurs after an appropriate trailing end (a correct trailing end) of a speech-duration, a trailing end to be detected is disadvantageously detected in regard of the correct trailing end due to an influence of a power of the extemporaneous noise.
It is to be noted that a countermeasure of reducing a trailing end detection time to be shorter than a time length from the correct trailing end to the extemporaneous noise can be considered for the problem. When the trailing end detection time is simply reduced, however, a word including a double consonant, e.g., “Sapporo” is detected as divided durations. That is, there is a problem that silence in a word cannot be discriminated from that after end of utterance.